The Internet is a loose network of connected computers spread throughout the world. A message can be sent from any computer on the Internet to any other by specifying a destination address and passing the message from computer to computer via a series of "hops." Each computer, or "node," on the Internet has a unique Internet address. When an intermediate computer receives a message in transit, the computer checks the intended destination of the message and passes it along accordingly.
The Internet is growing, in terms of both size and sophistication, at a rapid rate. In the past, most users of the Internet were academic, research, or institutional users; the Internet was primarily used at that time to transmit and receive electronic mail and network news and to allow transfer of computer files.
However, since the introduction of the World Wide Web (also known as the "Web" or the "WWW") several years ago, the Internet has begun to host increasing amounts of other types of data of general interest, namely representations of images, articles, etc.
The Web presents a graphical user interface to the Internet. "Web pages," often consisting primarily of text and graphical material, are stored on numerous computers, known as "Web servers," throughout the Internet. These Web pages are generally described, in terms of layout and content, by way of a language known as "HTML" (HyperText Markup Language). Any particular computer linked to the Internet can store one or more Web pages, i.e. computer files in HTML format, for access by users.
A software program known as a "browser" can be used to access and view Web pages across the Internet by specifying the location (i.e. Internet address) of the desired Web page, or more commonly, by "hotlinking" to Web pages. Common browsers are Lynx, NCSA Mosaic, and Netscape Navigator. The desired Web page is specified by a uniform resource locator ("URL"), indicating the precise location of the HTML file in the format "http://internet.address/directory/filename.html".
Hotlinking is accomplished as follows. The user first accesses a Web page having a known address, often on the computer located at the user's ISP (Internet Service Provider). The ISP is the organization providing Internet connectivity to the user. That Web page can contain, in addition to textual and visual data specified in HTML format, "links," or embedded information (in the form of URLs) pointing to the Internet addresses of other Web pages, often on other computers throughout the Internet. The user, by selecting a link (often by pointing and clicking with a mouse), can then access other Web pages, which can in turn contain further data and/or additional links. When a Web page is accessed, its information is transmitted from the remote computer, wherever in the world it may be located, across the Internet, to the user.
In recent times, the Web has begun to host highly sophisticated types of multimedia content, such as audio and video data. Various extensions to HTML, such as Netscape's EMBED tag, allow references to other data to be embedded into Web pages. Some browsers are not capable of handling data other than text and images. Other browsers can handle the data in various ways. NCSA Mosaic, for example, handles references to unknown types of data by allowing the data to be downloaded to the user's computer, and then optionally invoking an external program to view or manipulate the data. Recent releases of Netscape Navigator take the concept one step further: a browser extension, or "plug-in," can be automatically invoked to handle the data as it is received from the remote Web page. Other means, such as network program "applets" written in the Java language (or a similar language), can be used to extend the functionality of the browser environment or network.
Compared to first generation Web content, namely text and still images, audio and video data have extremely high storage and bandwidth requirements. In particular, video files can be very large, from approximately 10 megabytes to 10 gigabytes. In order to play video files at speeds approaching their recorded rate at a user's terminal, the files have to be delivered at a fast, constant speed. Too slow, and the image plays back slower than originally recorded. If the speed is uneven, then the video appears jerky, like an old-time movie. At present, it is difficult, if not impossible, to provide sustained high-speed transmission of large files over a multi-node link on the Internet. Because the data is often transferred from afar, many factors can cause the delay or even loss of parts or all of a transmission.
This attribute, combined with the rapid growth of the Web and the Internet in general, has led to several problems. There is now a high and increasing volume of Internet traffic caused by Web page access, and the demand for bandwidth already exceeds supply.
Furthermore, certain content on the Web is extremely popular. Because current Internet technology provides Web pages from specific or "dedicated" remote site or servers, the most popular sites are often overloaded. Furthermore, according to current Internet technology, each response to a user request is generally transmitted separately. In other words, if one hundred users request transmission of the same Web page at the same time, one hundred separate transmissions must be made to these users. Because many of these popular Web pages are often being transmitted across many nodes on the Internet, there can be substantial duplication, delays and lost requests, for both the requested data and other, unrelated data being transmitted over the same routes. If a Web server containing video data receives many simultaneous requests, its ability to transfer all of the files at full speed is impaired.
Accordingly, a need exists for a system capable of providing improved access to audio/video content on the Internet or another general purpose network. Such a system would take steps to ensure that content is delivered without delay or interruption to all users requesting it.
The prior art is primarily directed towards text or image database providers, and so-called "video on demand". These systems are not designed to store text and video or audio-visual data across multiple computer systems in a distributed network. The "video on demand" concept is based primarily on a host-client architecture for downloading real-time audio-visual data, in very large amounts at a very high speed. Such systems aim, for example, to provide full-length movies, with sound, to on-line subscribers. Typically, remote users communicate with large mainframe servers containing the audio-visual data. The host-client architecture of such systems stems from the desire to eliminate bandwidth limiting elements in the system by locating the video data solely on the provider's high-capacity system. The provider must then insure that hardware and software used to distribute this data is capable of the very high storage and transmission rates required, and is virtually error free, so that no perceivable data is corrupted or lost.
Known and proposed "video on demand" systems involve expensive and sophisticated computer and communication systems which are adapted to feed full length movies to attached subscribers "on demand." Such systems use a massively parallel computing architecture, in an attempt to adapt the multi-processing computing system to manage the monumental video data delivery requirements of hundreds of simultaneous users. Each multi-processing computer is a single "mainframe" computer and operating system with numerous intricately interconnected individual microprocessors. The massively parallel computers also have very high speed internal data buses with the capability of sustaining a significant but fixed level of internal data traffic.
Massively parallel systems present three distinct disadvantages: (1) reliability, (2) cost, and (3) they are not scalable. Since video data is highly storage intensive, a very large number of hard drives are required to sustain the system. This requirement substantially increases cost. Further, because the hard drive is generally the most unreliable aspect of any computing system, using a large number of hard drives contributes significantly to making the overall system more unreliable. Also, due to the centralized system's basic structure, it is not scalable.
Another system employing large mainframe servers to store the audiovisual data for delivery to a small number of users depends on reducing hard drive throughput by developing specialized hard drive interface software. This software determines how the computer's operating system uses the computer's hard drive. For example, multiple blocks of related data can always be stored sequentially, instead of randomly. Although this may lead to more effective data throughput rates, such systems have the ability to accommodate only about 40 simultaneous users, and are geared to in house, small scale, video distribution.
A limited or partial "distributed" architecture has been proposed, which would link multiple personal computers together in order to fashion a much larger monolithic functional unit. In this system, video data is distributed only to build a single, much larger source of digital video information. For example, a long video is assembled "on the fly" from separately stored pieces on different machines. Such a system might subsequently use ATM switch technology to merge the output of this array of computers into one or more continuous video streams.
By contrast, the invention provides a true or complete distributed architecture with increased reliability and the capability of supporting thousands of simultaneously attached users, at a fraction of the cost of the massively parallel system. In a preferred embodiment, the invention uses the existing Internet infrastructure, in conjunction with a network architecture as described herein, to achieve rapid and efficient delivery of audio/visual content to end users.
The invention not only distributes unlike databases (for example, a related but distinct "text database" and "audio-visual database") across the assorted computing and communication devices, but it also partitions and distributes data in a manner which maximizes the performance of the network as a whole.
In one embodiment of the invention, the user, a real estate agent, has the capability of receiving up-to-date audio-visual information about a listed property. Presently, a real estate agent spends hours researching relevant aspects of available property, to include, inspecting the property, taking photographs of the property, and accumulating information about the property. In fact, the typical agent sees less than 50 percent of the new homes listed because of time constraints. Additional time and effort is spent ascertaining the prospective buyer's desires, introducing the buyer to the range of communities available within a chosen region, researching properties that the potential buyer may be interested in, and then showing these properties to the potential buyer.
According to the invention, a realtor's time will be more effectively used on activities directly related to selling property, and not on time intensive, activities necessary to stay abreast with market conditions. For example, by being able to view the property on a video terminal the realtor will reduce significantly the time spent researching potential properties. The time spent visiting properties with the potential buyer is likewise reduced by being able to introduce the property to the buyer via the video clip. This allows the realtor to devote more time to closings and other administrative duties associated with selling the property. Also, having the video retrieval capability allows the realtor to constantly refresh the customer's memory without having to revisit the property.